TW201430488A - Method for separating photomask pattern - Google Patents

Abstract

A method for separating photomask pattern, including the following steps: First, a layout pattern is provided, wherein the layout pattern is defined to at least one critical pattern and at least one non-critical pattern. Next, a first split process is performed to split the critical pattern into a first pattern and a second pattern. A second split process is performed to split the non-critical pattern into a third pattern and a fourth pattern. Finally, output the first pattern and the third pattern to a first photomask, and output the second pattern and the fourth pattern to a second photomask.

Description

Masking method of mask pattern

The present invention relates to the field of semiconductor processing, and relates to a method of dividing a reticle pattern.

Optical lithography is an important part of semiconductor manufacturing. Its basic principle is very similar to that of chemical photographic technology. The patterned reticle image is projected onto the surface of the wafer by a high-precision optical system. (such as photoresist). After subsequent composite chemical reactions and process steps such as exposure, post-development bake, and dry/wet etching, complex wiring patterns can be formed on the wafer surface.

In the semiconductor process, as the required difference between the scale of the feature features and the wavelength used by the optical lithography becomes larger, the resulting wafer image will be quite different from the pattern on the original mask. In the past, in order to achieve the required pattern density, resolution enhancement technology has become a necessary technical means in semiconductor manufacturing. One well-known resolution enhancement technique is Optical Approximation Correction (OPC), which deliberately distort portions of the target photoresist pattern to form the desired line pattern on the wafer. Today, considerable time and computer computing in semiconductor manufacturing processes are used in the post-production steps of such line layouts.

In addition to the optical approximation correction technique described above, in order to use the same lithography technology to further reduce the size of semiconductor components to the deep submicron range, a process called double patterning has been developed as an overcoming size. A technical means of limiting costs while saving costs. One of the popular methods of the above double pattern That is double exposure lithography, the principle is to split a given layout pattern into two groups of patterns, each group using individual masks in individual exposures The process is defined and formed, and the two sets of patterns can finally form a line pattern to be superposed.

The biggest advantage of dual exposure lithography is that it can use existing lithography and machines to create denser, smaller pitch line patterns. However, in practice, there are still some problems to be solved in this technology. At present, the industry still needs to further improve the existing double exposure graphics splitting method.

One of the problems with the double exposure lithography technique is that the step of splitting the line layout pattern into two sets of patterns is mainly performed by a computer program. However, it is easy to have two sets of pattern assignments by the two sets of patterns completed by the program. The problem of uneven density, which in turn affects the yield of the exposure step.

In order to solve the above problems, the present invention provides a method for dividing a reticle pattern, comprising at least the following steps: First, providing at least one layout pattern, the layout pattern being defined as at least one critical pitch pattern and at least one non-critical spacing pattern, and then Performing a first dividing step, dividing each of the critical pitch patterns into a plurality of first patterns and a plurality of second patterns, and then performing a second dividing step, dividing each of the non-critical spacing patterns into a plurality of third patterns and a plurality of And a fourth pattern, and finally outputting each of the first patterns and each of the third patterns to a first mask, and outputting each of the second patterns and each of the fourth patterns to a second mask.

The difference between the present invention and the conventional reticle segmentation step is that a second segmentation step is further used to divide the non-critical pitch pattern that is not emphasized in the conventional step, thereby making the line by the second segmentation step. In the layout pattern, both the critical pitch pattern and the non-critical pitch pattern can be equally divided into two groups of patterns, thereby avoiding the problem of uneven distribution of the two groups of patterns, thereby improving the yield of the exposure step.

10‧‧‧ layout pattern

20‧‧‧critical spacing zone

22‧‧‧critical pattern

24‧‧‧ first pattern

26‧‧‧second pattern

30‧‧‧Non-critical spacing zone

32‧‧‧ non-critical pattern

32'‧‧‧ non-critical pattern

32"‧‧‧ non-critical pattern

34‧‧‧ third pattern

36‧‧‧ fourth pattern

42‧‧‧First segmentation mark

44‧‧‧Second segmentation mark

46‧‧‧ third segmentation mark

52‧‧‧First mask

54‧‧‧second mask

S01~S09‧‧‧Steps

W1, W2, W3‧‧‧ width

L1, L2, L3‧‧‧ length

FIG. 1 is a flow chart showing the steps of dividing a reticle pattern according to the present invention. Figures 2-6 show a top view of the layout pattern in each step.

The present invention will be further understood by those of ordinary skill in the art to which the present invention pertains. .

For the convenience of description, the drawings of the present invention are only for the purpose of understanding the present invention, and the detailed proportions thereof can be adjusted according to the design requirements. As described in the text for the relative relationship between the relative elements in the figure, it should be understood by those skilled in the art that it refers to the relative position of the object, and therefore can be flipped to present the same member, which should belong to the same specification. The scope of the disclosure is hereby stated.

Please refer to FIG. 1 . FIG. 1 is a flow chart showing the steps of dividing the reticle pattern according to the present invention. Referring to FIG. 2 to FIG. 6 simultaneously, FIG. 2 to FIG. 6 are schematic diagrams showing the layout pattern in each step. The step of splitting the mask of the present invention is as follows. First, a layout pattern 10 is input into a storage medium of a computer such as a computer system (step S01), and then a screening step is performed on the entire layout pattern 10 by using a computer system to define at least one critical spacing area in the layout pattern 10. 20 and at least one non-critical spacing region 30 (step S03), wherein the difference between the critical spacing region 20 and the non-critical spacing region 30 is defined as: the layout pattern 10 includes a plurality of sub-patterns, when a sub-pattern and When the spacing between adjacent sub-patterns is less than a minimum exposure interval, then the two sub-patterns are all defined as the critical pattern 22, and the group consisting of the critical patterns 22 is the critical spacing region 20; conversely, when a sub-pattern is When the distance between adjacent sub-patterns is greater than the minimum exposure pitch, the sub-pattern is defined as a non-critical pattern 32, and the group consisting of the non-critical patterns 32 is a non-critical pitch region 30. Therefore, each of the critical pitch regions 20 includes a plurality of critical patterns 22, and the non-critical pitch regions 30 include a plurality of non-critical patterns 32. The distance between each of the critical patterns 22 and the adjacent critical patterns 22 is less than a minimum exposure interval, and each of the non-critical patterns 32 and the adjacent non-critical pattern 32 The distance between this is greater than the minimum exposure pitch. Wherein, the minimum exposure interval is normal, and the reticle including the layout pattern 10 is in the subsequent exposure process, and the adjacent two patterns can be clearly distinguished and identified after exposure and development, and the minimum spacing allowed, For example, in the current 20 nm process, the minimum exposure pitch is about 118 nm. When the spacing between the two patterns is less than 118 nm, the two patterns may be joined together after the exposure and development steps of the two patterns. Therefore, under the normal one-shot development process, the critical pattern 22 is too dense, resulting in poor exposure performance, and may even cause the pattern after exposure to be indistinguishable. Therefore, after defining the critical pitch region 20, the present invention performs a first dividing step (step S05), and splits the critical pattern 22 in the critical spacing region 20 into two groups, as shown in FIG. 3, respectively. Defined as a plurality of first patterns 24 and a plurality of second patterns 26, and all of the first patterns 24 (indicated by diagonal lines) are preset to be divided into a mask, and all of the second patterns 26 are preset to be Split to another mask. Wherein, the distance between each of the first patterns 24 is greater than the minimum exposure interval, and the spacing between the respective second patterns 26 is also greater than the minimum exposure interval. Therefore, the split first pattern 24 and the second pattern 26 no longer have a problem that the interval between adjacent patterns is too small, resulting in failure of exposure.

The segmentation method shown in FIG. 3 is only one possible embodiment of the present invention, and the segmentation manner of the first segmentation step is not limited to that shown in FIG. 3, and may be changed according to actual needs, and only needs to be satisfied. The distance between the divided first patterns 24 is greater than the minimum exposure pitch, and the spacing between the respective second patterns 26 is also greater than the minimum exposure pitch, which is within the scope of the present invention.

In addition to the first dividing step, the method for dividing the mask pattern of the present invention further includes performing a second dividing step (step S07) for each of the non-critical spacing regions 30, wherein the method of dividing is as follows: Please refer to FIG. First, any non-critical pattern within the non-critical spacing region 30 (e.g., 32' in FIG. 4) is selected, and then a plurality of separate marks are placed along the selected non-critical pattern. For example, extending from a boundary of the non-critical pattern 32, when the segmentation mark touches an adjacent non-critical pattern (for example, 32" in FIG. 4), the original non-critical pattern 32' is defined. For a third pattern 34, the non-critical pattern 32" touched by the segment marks is defined as a fourth pattern 36. Then, the non-critical pattern 32" that is touched is selected to repeat the above step, and the non-critical pattern that is touched with the division mark and has not been defined as the third pattern 34 or the fourth pattern 36 is defined as A pattern that is different from itself. For example, if a non-critical pattern has been defined as a third block, adjacent to it, other non-critical patterns touched by the split mark are defined as the fourth block. Or, conversely, if a non-critical pattern has been defined as a fourth block, adjacent to it, other non-critical patterns touched by the divided marks are defined as the third block. Repeat the above steps until it is located. All non-critical patterns 32 in the non-critical spacing region 30 are defined, so each of the above-mentioned segmentation marks will be located between the two non-critical patterns. As for the partial non-critical pattern, the segmentation marks extending outward from the boundary thereof are Without touching any other adjacent non-critical patterns (such as the non-critical pattern in the upper left corner of FIG. 4), the non-critical pattern can be arbitrarily defined as the third block or the fourth block. It is understandable that Figure 4 The division of the third pattern and the fourth pattern is only one of the possibilities of the present invention, and the present invention is not limited thereto, and the outwardly extending direction is preferably any boundary of the parallel non-critical pattern 32'. For example, it can be horizontal or vertical.

The segmentation mark of the present invention comprises a plurality of different geometric shapes. For example, in FIG. 4, three different segmentation marks in the present embodiment are illustrated, which are respectively labeled as a first segmentation mark 42, a second segmentation mark 44, and a third segmentation mark. 46. The first segment mark 42 has a rectangular shape, and its width (W1) is equal to one side of the non-critical pattern. When a non-critical pattern and its adjacent non-critical pattern are arranged in parallel in a horizontal or vertical direction, the first segmentation is performed. The mark 42 is placed at the boundary of the non-critical pattern, that is, it is possible to contact adjacent non-critical patterns. When the non-critical pattern and the adjacent non-critical pattern are horizontally or vertically misaligned, it is possible to select the second dividing mark 44 or the third dividing mark 46 to be disposed at the boundary of the non-critical pattern. In this embodiment, the second The division mark 44 is extended from the boundary of the non-critical pattern in the horizontal direction, and its width (W2) is larger than the boundary of the non-critical pattern, and the third division mark 46 is extended from the boundary of the non-critical pattern to the vertical direction, and its width ( W3) is larger than the boundary of the non-critical pattern, and thus can contact adjacent non-critical patterns located in an oblique direction. In addition, changing the length of each of the divided marks can adjust the division of the non-critical pattern 32. For example, in the present embodiment, the lengths of the first divided mark 42, the second divided mark 44, and the third divided mark 46 ( L1 L2, L3) is preferably less than a predetermined value, for example, 2 micrometers (μm), so that the spacing between the divided third patterns 34 is greater than 2 μm, and the divided fourth patterns 36 are mutually The spacing between them is also greater than 2 μm. Of course, the division mark of the present invention is not limited to the above, and the width, the length and the shape can be changed according to actual needs. In addition to the rectangle, a circle, an ellipse, or any irregular shape can be freely selected as the division mark.

It should be noted that, in the foregoing embodiment, after the first dividing step S05 is performed, the second dividing step S07 is performed, that is, the critical pattern 22 in each critical spacing region 20 is first divided, and then each non-critical spacing region 30 is divided. The non-critical pattern 32 in the middle. However, the present invention is not limited thereto, and after the critical pitch region 20 and the non-critical pitch region 30 are defined, the second dividing step S07 is performed first, and then the first dividing step S05 is performed, that is, the non-critical spacing regions 30 are first divided. The non-critical pattern 32 in the sub-dividing of the critical pattern 22 in each critical spacing region 20 is also within the scope of the present invention. Subsequently, appropriate optical proximity correction (OPC) may be selectively performed on the first pattern 24, the second pattern 26, the third pattern 34, and the fourth pattern 36.

Finally, all the first patterns and the third patterns of the layout pattern 10 in the computer system are output to a first mask, and all the second patterns and the fourth patterns are output to a second mask (step S09). As shown in FIGS. 5-6, the first mask 52 includes a first pattern 24 and a third pattern 34, and the second mask 54 includes a second pattern 26 and a fourth pattern 36. In addition, all the first patterns and the fourth patterns of the layout pattern 10 in the computer system may be output to the first mask, and all the second patterns and the third pattern are output to the second mask, as long as the first The pattern may be present on a single reticle when it is different from the second pattern (or the third pattern and the fourth pattern). Then, the first photomask 52 and the second photomask 54 are sequentially used for the two exposure and development processes, and the combination of the patterns on the two masks is the complete pattern of the layout pattern 10.

The invention is characterized in that, in the first dividing step S05, the pattern with the original exposure pitch too small can be split into two different patterns, so that the spacing between the patterns can be effectively increased, and the problem that the exposure interval is too small is avoided, and the problem is eliminated. In addition, since the present invention further has the second dividing step S07, even the pattern located in the non-critical spacing region 30 is equally divided into two groups of patterns, such that When the pattern is output to the mask, the pattern distribution on the two masks can be evenly distributed, and it is not easy to be unevenly distributed due to the pattern, so that the difference in light intensity between the two masks is too large during the double exposure process. problem.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

S01~S09‧‧‧Steps

Claims (10)

A method for dividing a reticle pattern includes the steps of: providing at least one layout pattern, and defining the layout pattern as at least one critical pitch region and at least one non-critical spacing region, wherein the critical spacing region includes a plurality of critical spacings a pattern, the non-critical spacing region includes a plurality of non-critical spacing patterns; performing a first dividing step, dividing each of the critical spacing patterns into a plurality of first patterns and a plurality of second patterns; performing a second dividing step, Dividing each of the non-critical pitch patterns into a plurality of third patterns and a plurality of fourth patterns; outputting each of the first patterns and each of the third patterns to a first mask, each of the second patterns and each of the first patterns The four patterns are output to a second photomask. The method for dividing a reticle pattern according to claim 1, wherein each of the first patterns is spaced apart from each other by a minimum exposure interval. The method for dividing a reticle pattern according to claim 1, wherein each of the second patterns is spaced apart from each other by a minimum exposure interval. The method for dividing a reticle pattern according to claim 1, wherein the distance between the critical pitch patterns is less than a minimum exposure interval, and the distance between the non-critical pitch patterns is greater than the minimum exposure interval. The method for dividing a reticle pattern according to claim 1, wherein the second dividing step further comprises defining a plurality of separator marks between the non-critical pitch patterns in the non-critical pitch region, and One of the two non-critical pitch patterns on either side of the split mark is defined as the third pattern, and the non-critical pitch pattern on the other side is defined as the fourth pattern. The method for dividing a reticle pattern according to claim 5, wherein a distance between each of the divided marks is less than a predetermined value. The method for dividing a reticle pattern according to claim 5, wherein each of the division marks is located at a boundary of each of the non-critical pitch patterns and extends outward. The method for dividing a reticle pattern according to claim 5, wherein each of the division marks has a rectangular shape and is parallel to each of the non-critical pitch patterns. The method for dividing a reticle pattern according to claim 5, wherein each of the division marks has a rectangular shape, and is offset from each other in a horizontal direction with each of the non-critical pitch patterns. The method for dividing a reticle pattern according to claim 5, wherein each of the division marks has a rectangular shape and is offset from each other in a direction perpendicular to each of the non-critical pitch patterns.